Brush-holder.



.E. W. STULL.

BRUSH HOLDER.

APPLIOATION FILED JUNE 7, 1909.

Patented June 23, 1914.

amxqv 51m UNITED STATES PATENT OFFICE.

EMMETT W. STULL, or MILWAUKEE, WISCONSIN, ASSIGNOR BY MESNE ASSIGNMENTS,

n10 ALLIs-oHAL'MEns MANUFACTURING COMPANY, A CORPORATION or DELA- WARE.

BRUSH-HOLDER.

Specification of Letters Patent.

Patented J nne 23, 1911.

To all whom it may concern: 7

Be it known that I, EMIMETT 1V. S'rULL, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Visconsin, have invented certain new and useful Improvements in Brush- Holders, of which the following is a full, clear, and exact specification.

My invention relates to brush-holders for dynamo-electric machines.

The object of my invention is to provide a simple and inexpensive brush holder com prising means whereby the pressure exerted on the brush is practically constant at all times.

More specifically considered my invention consists in means whereby the pressure 011 a brush is kept constant by means of a resilient clement, preferably a. coil spring, which has its moment arm gradually increased to counter-act tendency of the spring to weaken as it is stretched out. 7

My invention further consists in the details of construction, arrangement of parts, and combinations of elements described in the specification and set forth in the appended claims In the accompanying drawing Figure 1 is a perspective view of a brush-holder embodying my invention; and Fig. 2 is a partial sectional view of my brush-holder showing more in detail the arrangement of the various elements.

The frame 10 of my brush-holder consists of a central Web 15 which supports an integral plate 11. against which. a carbon brush 12 rests. The plate is further sup ported by ribs 14 which also stiffen the whole supporting frame. The carbon brush can be fastened to the smooth surface of the plate by any desired means, for instance, by a band 30 passing around the brush and a portion of the frame and secured thereto. Flexible conductors 81 are secured to the band 30 and electrically connected to the brush by rods 32. The frame is also pro vided with an opening 13 for the reception of a supporting stud, the opening being located close to the bearing surface of the carbon brush thus preventing the undesirable results due to vibration. The brush-holder is held firmly on this stud by a set-screw 36 which passes through a threaded portion of the frame. At the back end of the supporting frame is a finger 16 to which a pressure arm 17 is pivoted at 18. A regulating screw 19 passing through a tapped portion of the finger 16 is mechanically fastened to a collar 20 having a loose fit with said screw and which has an extended portion provided with a hole for the reception of a pin. A guide rod 21 having a forked end is pivoted to the collar 20. The arm 17 consists of two sheet metal curved or arched side pieces held at a predetermined distance apart by spacing and supporting members 23 and 27 respectively, which are riveted to said side pieces. The free end of the arm is provided with a loose sleeve or roller 24; which bears upon the brush. The outer end of the pressure arm is held evenly against the brush by a spring which is mounted on the guide rod 21. The free end of the guide rod 21 fits loosely and passes through an opening in one of the spacing and supporting members 23. As the arm is gradually forced down upon the carbon brush 12, the spring gradually stretches and thereby weakens. However, at the same time the moment arm, through which the spring acts, increases and keeps the pressure to which the brush is sub ject practically constant. For example, the pressure arm as shown in Fig. 2 bearing upon the carbon brush 12 is in its normal position. The center line of the guide rod and spring is shown at aa. The effective moment arm of the spring is represented by the distance TVhen the pressure arm is lowered the center line a -a is shifted to a new position, as shown by the line a-a. The spring is extended and thus weakened, but at the same time the effective moment arm is increased from a distance represented by w to a distance represented by at. It is therefore very clearly seen that there is an equalizing effect tending to keep the pres sure transmitted through the pressure arm and to which the carbon brush is subjected, practically constant. If it is desired to increase the pressure on the carbon brush this effect can be accomplished by increasing the moment arm, through which the spring acts, by screwing upwardly the regulating screw 19. The pressure can also be decreased by lowering the regulating screw.

The spring 25 serves a double purpose, to hold the pressure arm against the brush when desired, and to hold it away from the brush when the latter is to be replaced or adjusted. Between these two extreme posiand scope of my invention.

tions of the pressure arm there is a critical point. This critical point occurs when the three points 0, (Z, and e are in aline nent. The arm is prevented from flying too far back by the engagement of the forked end of the guide rod 21 with a shoulder 26 on the collar- 20. The spring here shown acts as a compression spring and can be relied on more, acting in this capacity than in any other, for it is practically impossible for it to reach its elastic limit or go beyond the same in thiskin'd of service. On the other hand, a spring which is used in such a way as to be subjected to tension is very apt to be stretched out beyond its elastic limit and thereby be permanently weakened. The compression spring is very neatly mounted between the side members of the pressure arm and is thereby protected and requires no extra space. v

Many modifications of the precise arl raiigement here shown and described may be made and I aim to cover all such modifications which do not depart from the spirit lVhat'I claim as new is I j 1. In combination, a brush-supporting 1 member, a fulcrum adjustably fixed thereon, a follower pivoted to the supporting 1nem her, and a spring acting between the fol lower and the fulcrum to effect rotation of the follower. I 2. In combination, a bruslrsupporting member, a fulcrum mounted thereon and adjust'able relatively thereto, a follower pivi' oted to said member, and resilient means acting between the follower and the fulcrum to cause a movement of the follower. I

3. In combination, a brash-supporting member, a follower pivoted thereto, said brush-supporting member being provided with a spring restraining means, and a coml ilfeSsitfll spring acting between said springrestraining means on the brush-supporting member and the follower, and said spring restraining means on the brush-supporting member being adjustable relatively to the axis of said follower and causing said spring to exert ,an approximately constant turning moment on the follower about its axis in its various operative positions.

4. In combination, a brush-supporting member, a spring retaining means thereon, a follower pivoted to said supporting member. and resilient means between said follower and said spring retaining means, said spring retaining means being adjustable relatively to said supporting member to vary the degree of change in the turning moment of said spring on said follower as said follower moves into different operative positions.

Milwaukee, Wis, May 19, 1909.

In testimony whereof I aflix my signature, in the presence of two witnesses.

EMMETT IV. ST ULL.

\Vitnesses CHAS. LJBYRON, Ron. E. S'I'ULL.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, I). C. 

